• Composites Research
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• 제18권3호
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• pp.7-13
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• 2005

본 논문에서는 하이브리드 복합재 철도차량차체에 적용되는 복합적층판에 대한 저속충격시험을 수행하였다. 이를 위해 2.4J, 2.7J 및 4.2J의 세 가지 충격에너지 조건에서 세 가지의 다른 적층구조를 갖는 적층판에 대한 저속충격시험을 수행하였다. 시험에 적용된 직조된 카본/에폭시 적층판의 크기는 $100mm\times100mm$ 이다. 충격시험 후 충격하중이력, 흡수된 에너지 및 손상면적 등이 각 충격에너지와 적층순서에 따라 고찰되었다. 손상면적은 육안검사와 C-scan을 이용하여 동시에 검사하였다. 시험결과 흡수된 에너지는 $[fill]_8$, 적층판이 가장 높았고 $[fill_2,/warp_2)_s$ 적층판이 가장 낮았다. 또한 손상면적은 $[fill]_8$, 적층판에서 가장 넓은데 이것은 상대적으로 흡수에너지가 높기 때문이다.

• Journal of Welding and Joining
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• 제22권6호
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• pp.57-63
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• 2004

Fracture toughness is an important parameter in designing offshore structures to ensure resistance to fracture at various temperatures. In this study, a series of experiments is carried out to obtain fracture toughness values (CTOD) of API 2W Gr.50B, welded using FCAW(Flux Cored Arc Weld). In particular, a comparison of absorbed impact energy and CTOD values are made with respect to two different welding groove shapes; double-V-groove and double-bevel-groove. Charpy impact tests are performed for specimens sampled near the root gap, and CTOD tests are carried out for three point bending specimens having the notch at weld zone. While Charpy impact test result is determined to be a good qualitative measure of fracture toughness, no quantitative correspondence between impact absorbed energy and CTOD values was found. Based on the experiment, it is observed that double-V-groove welds give lower transition temperature than those of double-bevel-groove.

• Composites Research
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• 제13권4호
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• pp.75-82
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• 2000

유리섬유/에폭시 복합재료로 피막한 유리판의 표면파괴거동을 연구하기 위하여 미소강구 충격실험을 수행하였다. 본 연구에서는 다섯 종류의 재료, 단순소다유리판(soda-lime glass plates), 유리섬유/에폭시박막(glass/epoxy lamina)을 1층 접착, 비접착한 시편과 박막을 3층 접착, 비접착한 시편을 사용하였다. 충격속도 범위 40∼120m/s에서 유리판 배면에서의 최대 응력과 흡수파괴에너지를 측정하였다. 충격 속도증가에 따라 링균열, 콘균열, 레이디얼 균열이 시편 내부에서 발생하였다. 복합재료 박막으로 피막한 결과, 소다유리판의 균열은 현저히 감소하였으며 측정한 최대 응력과 흡수파괴에너지를 이용하여 표면 파괴거동 특성을 평가할 수 있었다.

• 한국강구조학회 논문집
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• 제15권2호
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• pp.147-157
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• 2003

최소유지관리의 LCC관점에서 강구조물에의 적용이 증가하고 있는 내후성강재를 대상으로 Mill Sheet를 수집하고 이를 통계적으로 분석하여 화학성분, 기계적성질, 용접성지수, Weathering Index 및 충격흡수에너지에 대해 정량적으로 조사하였다. 본 연구결과 국내에서 생산되고 있는 내후성강재의 화학성분, 기계적 성질 및 충격흡수에너지는 분산의 폭이 약간 크게 나타났으며 KS에서 규정하는 기준값을 충분히 만족하고 있는 것으로 나타났다. 또, 용접성지수 및 Weathering Index는 일본 도로교시방서 및 ASTM의 기준을 만족하고 있는 것으로부터 국내 내후성강재의 품질을 확인 할 수 있었다.

• 동력기계공학회지
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• 제19권5호
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• pp.73-79
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• 2015

The effects of hydrogen charging on the mechanical properties of 304 stainless steels were investigated in conjunction with the detailed examinations of their fracture modes. The dependence of the absorbed impact energy and the surface hardness of the 304 stainless steels on the hydrogen charging time was characterized. The tensile properties of the 304 stainless steels by the variation of cross-head speed were also evaluated at the room temperature. The hydrogen charging was performed by an electrolysis method for all specimens of the 304 stainless steels. The mechanical properties of the 304 stainless steels exhibited the sensitivity of embrittlement due to a hydrogen charging. The correlation between mechanical properties and fracture surfaces was discussed.

• 한국안전학회지
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• 제23권6호
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• pp.34-37
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• 2008

The composite materials are widely used in the many applications of industry as well as aerospace field because of their high specific stiffness and strength which benefits the material and provides potential energy savings. However, composite materials also have a low property about external applied impact. In this paper, impact tests were conducted on different sample types(glass, carbon and kevlar composite) to obtain information such as absorbed energy and composite deformation using an instrumented impact test machine (DYNATUP 8250). 3 type samples were compared to experimental results. The data from impact test provided valuable information between the different type samples by wet lay up. This paper shows results of that kevlar composite has larger absorption energy and deformation than others.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.330-335
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• 2004

The needs of walking assistive device such as the Ankle Foot Orthosis (A.F.O.) are getting greater than before. However, most of the A.F.O. are generally imported rather than domestic manufacturing. The major reason of high import reliability is the rack of impact properties of domestic commercial products. Therefore, this research is going to focus on the evaluation of impact properties of the A.F.O. which has the high import reliability. Unfortunately, these kinds of researches are not performed sufficiently. This research is going to evaluate impact energy behavior in composite materials such as the glass/epoxy (S-glass, $[0/90]_{2S}$) and the aramid/epoxy (Kevlar-29, woven type, 8 ply) of ankle foot orthosis. The approach methods were as follows. 1) The history of impact load and impact energy due to the various velocities. 2) Relationship between the deflection and damage shape according to the impact velocities. 3) The behavior of absorbed energy and residual strength rate due to the various impact velocities.

• 대한기계학회논문집A
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• 제33권1호
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• pp.64-71
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• 2009

In this paper, a study on low-velocity impact response of honeycomb sandwich panels was done for the changes of impact location and core fabrication angles. The test specimens were made of glass/epoxy laminate facesheet and aluminum honeycomb core. Square samples of 100mm and 100mm sides were subjected under low-velocity impact loading using instrumented testing machine at three energy levels. Impact parameters like maximum force, time to maximum force, deflection at maximum force and absorbed energy were evaluated and compared for the changes of impact location and core fabrication angle. The impact damage size were measured at facesheet surface by 3-Dimensional scanner. Also, sandwich specimens after impact test were cut to analyse the failure mode.

• Journal of Welding and Joining
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• 제28권5호
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• pp.69-74
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• 2010

Irradiation behavior of the reactor pressure vessel SA508 class 3 steel weld metals was examined by Charpy V Notch impact specimens. The specimens were exposed to a fluence of $2.8{\times}1019$ neutrons(n)/$cm^2$(E>1 MeV) at $288^{\circ}C$. The irradiation damage of weld metal was evaluated by comparison between unirradiated and irradiated specimens in terms of absorbed energy and lateral expansion. The specimens for neutron irradiation were welded by submerged arc welding process at a heat input of 3.2 kJ/mm which showed good toughness in terms of weld microstructure, absorbed energy and lateral expansion. The post-irradiation Charpy V notch 41J and 68J transition temperature elevation were $65^{\circ}C$ and $70^{\circ}C$, respectively. This elevation was accompanied by a 20% reduction in Charpy V notch upper shelf energy level. The lateral expansion at 0.9mm irradiated Charpy specimens showed temperature elevation of $65^{\circ}C$ and was greatly decreased due to radiation damage.

• 한국생산제조학회지
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• 제21권6호
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• pp.892-896
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• 2012

CFRP composites with light weight, high strength, and high elasticity by comparing with metal are widely used rather than previous steel plates. However, CFRP composite material has the weakness at hydrothermal and collapsed impact environment. Especially, moisture absorption into composite material can change molecule arrangement and chemical properties under hydrothermal environment. And static collapse experiment is the research in the differences of absorbed energy and deformation mode between moisture and non-moisture absorbed specimens. This study is compared and analyzed on the progress change of moisture absorption ratio after setting up the temperatures of 60 and 80 degrees C in order to comprehend how the change in the temperature influences on moisture absorption status inside CFRP composite materials.